Bubbles are sweet

A lot of effort is going into nanomaterials made out of hexagons of linked carbon atoms: buckyballs (spheres), graphene (flat sheets), nanotubes (sheets rolled into cylinders). The combination of great mechanical strength, very high conductivity, and dirt cheap raw material is enticing. The trouble with these nanomaterials is that they are, well, nano: tiny objects that are difficult to assemble into anything macroscopic. It’s hard for instance to connect a sheet of graphene one atom thick to a wire, even the tiny sort in integrated circuits. I reported some time ago on buckystring, superfine thread spun out of nanotube fibres, but SFIK it’s stayed in the lab. Carbon-fibre composites are widely used in aircraft, but the reinforcing fibres are not composed of nanotubes. Hence the search for more manageable 3D forms.

Enter the Japanese materials scientist Yoshio Bando and his Chinese colleague Xuebin Wang.

Inspired by the ancient food art of â€˜blown sugarâ€™, Bando and his team reasoned that the strutted, coherent nature of conjoined bubbles would lend itself to strength and conductivity if graphene could be structured in the same way. The researchers created a syrup of ordinary sugar and ammonium chloride. They heated the syrup, generating a glucose-based polymer called melanoidin, which was then blown into bubbles using gases released by the ammonium. [….]
As the bubbles grew, the remaining syrup drained out of the bubble walls, leaving within intersections of three bubbles. Under further heating, deoxidization and dehydrogenation, the melanoidin gradually graphitized to form â€˜strutted grapheneâ€™: a coherent 3D structure made up of graphene membranes linked by graphene strut frameworks, which resulted from original bubble walls and intersectional skeletons respectively. [ ….] The resulting 3D graphene is robust [it can be compressed to 80% and bounce back] and maintains excellent conductivity.

They are talking about capacitors, but I dare say people will find other uses as well.

Bando is already making his buckyfoam in gramme quantities. He even quotes a cost: $0.5 a gramme. Since sugar costs $1.50 a kilo retail and lab-grade ammonium chloride $22 (fertiliser grade is a fraction of that), the main cost is the heating.

I obviously can’t guarantee that this is the breakthrough to usable buckymaterials. It must now be the front runner. Plainly there are hurdles ahead. Can you make large homogenous blocks of buckyfoam? Can you make thin sheets? If so, can you cut them with lasers into wires? I post news of this mainly to celebrate the strange ways of the creative imagination.

The street sugar-blowers of Asia blow very thick-walled bubbles, but not foams. This video shows that it is possible to blow short-lived sugar bubble clusters, but not comparable to the polygonal structures you can achieve with soap. Bando and Wang are not on oath about their inspiration, and I suspect soap and small children come in to it too.